The principle also applies to drone strikes, etc.
In warfare you can kill your enemy without trial, and that's why we've called this a "war on terror" - it's very deliberate. It removes the need for the judicial process in many people's eyes.
But in reality these terrorists are criminals. Criminals in this country aren't routinely executed by special forces/drone strikes, etc. Maybe in the US, but hey...
Have we removed the need for any kind of judicial oversight, rule of law, etc? A terrorist can be killed like an enemy combatant in times of war. The problem is now that you can seemingly apply the term "terrorist" to any number of people... who decides? What are the rules for determining who can just be killed without judicial process and who must be given a trial, etc?